Study On Preparation Of Immobilized Lipase On The Core-Shell Type Magnetic Mesoporous Composite Materials And Catalytic Performance Of Ester-Ester Interesterification Of Oils And Fats

The core-shell type magnetic mesoporous composite materials HAP-γ-Fe2O3,Fe3O4@MCM-41 were prepared,and treated with 3-aminopropyltriethoxysilane as immobilization materials.Then Candida rugosa lipase was immobilized onto the amino-functionalized magnetic HAP-γ-Fe2O3,Fe3O4@MCM-41 composites by using glutaraldehyde as a coupling reagent.On the other hand,the magnetic Fe3O4@MCM-41 composites were modified by the ionic liquid and then the immobilized lipase was prepared through typical adsorption.The as-prepared supports and the immobilized lipase microsphere were characterized by means of enzyme activity assays,transmission electron microscopy(TEM),X-ray powder diffraction(XRD),Fourier transform infrared(FT-IR)spectra,vibrating-sample magnetometer(VSM)and nitrogen adsorption-desorption techniques.The characterization results showed that the magnetite nanoparticles were well coated with the HAP or MCM-41 silica with the formation of core-shell structured materials,and moreover the lipase was successfully immobilized on the core-shell structured support.Besides,the immobilized lipase behaved superparamagnetic and showed excellent response at applied magnetic field.Further,the immobilized lipase proved to be easily separated from the reaction mixture by applying an external magnetic field.The catalytic performance of HAP-γ-Fe2O3-lipase was tested in the intersesterification of soybean oil and palm stearin system or soybean oil and methyl stearate system in a batch reactor.The enzyme immobilization conditions,reaction conditions and the catalytic regioselectivity were studied.The results showed that the optimum enzyme immobilization conditions was:the ratio of free lipase to carrier,2:1;the immobilization temperature,25℃;pH 7.0 and the immobilization time,10h.With the optimum immobilization conditions,the reaction conditions of soybean oil and methyl stearate system were tested.When the substrate ratio was 1:4,temperature was 45℃ and the amount of catalysts was 25%,the relative conversion of methyl stearate came to a head.In addition,the immobilized lipase has certain selectivity at sn-1,3 of the triacylglycerol according to the experimental results.For the soybean oil and palm stearin system,the FA profiles and TAG compositions of the interesterified products were changed obviously after the enzymatic interesterification reaction.The slip melting point(SMP)of the interesterified products was lower then that of the original blend,and the intersesterification reaction led to the change in the microstructure of the product.In the study,a core-shell structured Fe3O4-MCM-41 nanocomposites was prepared,and then Candida rugosa lipase was covalently bound to the core-shell magnetic material by using glutaraldehyde as a cross-linking reagent.The catalytic performance of the bound lipase was tested in the intersesterification of soybean oil and lard in a batch reactor.It was shown that the FA profiles and TAG compositions of the interesterified products were changed obviously after the enzymatic interesterification reaction.The slip melting point(SMP)of the interesterified products was lower than that of the original blend,and the intersesterification reaction led to the change in the microstructure of the product.The catalytic performance of IL-Fe3O4@MCM-41-lipase was tested in the intersesterification of rice bran oil and palm stearin system.Physical and chemical properties such as melting point and crystallization of the products were investigated.The FA profiles and TAG compositions of the interesterified products were changed obviously after the enzymatic interesterification reaction.The results showed that the interesterified products had lower melting point,the crystallization of product was smaller than the original blend.